Adding extensions to .gitignore
Including support to exceptions

Initial support to exceptions is now available. There are still some
header files to be adjusted (removing asserts and replacing them with
proper exceptions), but this should give a basis to other parts of the
project that require adequate handling of errors.
Fixing matching of parentheses
Finishing exception support to the rest of the source.

Important: As of right now, error handling is still prone to bugs. Therefore, fetching of this branch is discouraged.
Adding a new exception file for Gabriel
Fixing a small error
Merging with python-ext
Making the example slightly more complete
Making things merge
For Gabriel --- New exceptions
A couple more fixes
Fixing some incoherences

Code does not compile yet.
Fixing the bugs that Gabriel was seeing
Extending AnjuException support to other files

There are no standalone try/catch blocks, having these being properly
translated into their corresponding macros. However, bringing exception
support to files that didn't make use of asserts in the legacy code is
still needed to be done.
Making exceptions standard --- they are implemented in most places now
Putting in changes from Gabriel into Anna's branch